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J I f " t J I J ,I I j 1 t I 1 I 'it I I 00155~ ninety-eight of the three hundred-eleven-bird species in the basin depend in some way on the riparian habitat. Ninety-three of these are directly dependent on this zone for reproduction and survival. There are also ninety-nine species of mammals, thirty-four species of reptiles, fourteen species of amphibians and a variety of aquatic invertebrates permanently resident in the San Juan River basin. Some parts of the river also provide habitat for migrating raptors and other birds including bald eagles, peregrine falcons and whooping cranes. Approximately 500,000 waterfowl winter along the San Juan River and its riparian habitat. (Petty et al. 1992) There are fifty species of fish found in the San Juan basin, sixteen of which are native. Endangered fish such as the Colorado squawfish and razorback sucker, and roundtail chub, a category 2 candidate species, require backwater habitat and low flow channel areas for spawning and nursery areas. Fish and wildlife habitat requirements in the Basin are in competition with the more than 50,000 people that use scarce water supplies for agricultural, industrial and domestic ,purposes. Contamination of this waterway is not only a major concern for the fish and wildlife resources in the basin but also for the human population. All public water utilities that provide water to 2,500 people or more utilize surface waters. Those smaller communities which use groundwater from the shallow alluvial deposit in the basin can have their water supplies contaminated by anthropogenic activity in the area. (Petty et al. 1992) Eisler (1987) states several factors which influence uptake, retention, and translocation of PAHs by aquatic organisms. Most species of aquatic organisms will rapidly accumulate PAHs from their surrounding environment, but will also metabolize quite rapidly according to species specific metabolizing factors. This suggests that for any given water system, each species will accumulate different quantities of PAHs and any resultant deleterious effects will vary. A study of American lobsters by Sirota and Uthe (1 981), showed higher PAH concentration in large lobsters than in small lobsters, implying a correlation in age or body size to PAH accumulation dynamics. Johnston and Baumann (1989) suggest that certain species of fish may serve as better indicators of PAH contamination than others. They also state that species with relatively low biliary concentrations may exhibit a higher frequency of tumors with more metabolites retained as adducts than a species with high biliary concentrations and low tumor frequency. Johnston and Baumann suggest combining the HPLC/florescence method with histopathological and sediment analyses to determine source and extent of exposure to freshwater fish populations. The ability of many organisms to convert PAH to various metabolites such as phenols and dihydrodiols, leads to prOblems in assessing exposure of these animals to PAH compounds using analysis of tissue samples. However, using a HPLC/ florescence method to determine concentration of biliary PAH will give an indication of current levels of exposure (McDonald et al. 1990; Johnston and Baumann 1989; Krahn et al. 1987, 1986a, 1984). Species specific hepatic enzymatic variations determine that some fish species will show relatively high metabolites in bile versus other species. This makes it difficult to select one species as a surrogate for another (i.e. flannelmouth sucker for Colorado squawfish) for estimating PAH-related health threats. Dr. Susan J. McDonald of the Geochemical and Environmental Research Group at Texas A&M University (GERG) has stated that she has observed flannelmouth suckers to exhibit relatively low metabolite levels, while species of catfish seem to be more sensitive to PAH and will show higher metabolite levels (McDonald pers. comm. 1993). Therefore, a species such as black bullhead (lcta/urus me/as) or channel catfish (lcta/urus,punctatus) could be used in further studies analyzing bile for PAH metabolites. However, these species are not found throughout the entire San Juan River basin. On the other hand, the flannelmouth sucker, which exhibits a much lower tendency to produce concentrations of PAH-related bile metabolites consistent with the concentrations present in water and/or sediment, is nearly ubiquitous throughout the Basin. Dr. McDonald has suggested that hepatic enzymatic assays might help normalize 2